Part of being the age you are, Samuel, is that you are learning to navigate more mature/complex friendships. And since people your age mature at different rates, that can be some pretty rocky navigation. Chances are your friends are maybe a little bit jealous of the fact that you are losing weight and getting stronger. I can tell from your other posts that parkour is becoming really important to you and you are showing some real dedication, which takes a very strong person. So your friends may be a little intimidated by this maturity you're showing, and they're dealing with it by calling you out on it.
But in the end all you can do is lead by example. Some may eventually come along with you and some may not, that is how friendships go. So just keep up with your training and what feels right to you. Let your friends know that their comments and behavior bother you, and leave it at that. If they keep it up, no need to make a big drama about it, just find some new friends (I know it can seem scary to do that, especially if you have been friends with those guys for a long time). But just find someone new to sit with at lunch, to start with, and see where it goes.
Eventually your friends will wonder why you "ditched" them, and you can tell them, "Because you guys were bothering me, and I asked you to stop, and you didn't. You weren't being a friend to me." But always leave the door open to them to still be friends if they eventually come around to understanding. Hostility will just make it worse.
Hope that helps. Good luck!
